The invention relates to a tangential belt drive for a plurality of spindles which are arranged in a row and are part of a spinning or twisting machine having pressure rollers which each are arranged approximately in the center between two spindles and deflect a tangential belt in the direction of these two spindles.
A tangential belt drive of the initially mentioned type is known on the basis of JP-AS 59-51606. In each case, one pressure roller is assigned to two spindles. In certain operating conditions, it is necessary to interrupt the drive. For this purpose, it is known in the case of a similar tangential drive according to FR-A 21 10 247 to provide lift-off rollers by means of which the tangential belt may be lifted off the pertaining spindles. Brakes are then simultaneously applied to the spindles. Lift-off rollers of this type result in increased expenditures and also subject the bearing of the pressure rollers to an additional load.
In the case of another known tangential belt drive according to DE-OS 16 85 951, a pressure roller, which is arranged in proximity of the spindle, is assigned to each of the spindles. This pressure roller can be moved away from the pertaining spindle in such a manner that the belt deflection is diminished and thus the driving force is reduced. The spindle may then be braked.
An object of the invention is to provide a tangential belt drive of the initially mentioned type in which, particularly for the purpose of braking, the driving force may be reduced to one spindle without the requirement of lift-off rollers which lead to an increased load on the pressure rollers.
This object is achieved by the fact that the pressure rollers are each held by means of a holding device in such a manner that when the pressure roller is in an operative position they can be moved in the direction toward each of the two spindles which are assigned to them, approximately in parallel to the direction of the course of the tangential belt.
By means of this construction, it is achieved that, in each case, one of the two spindles is largely relieved of the load by the tangential belt by means of a corresponding movement of the pressure roller, while the load with respect to the other spindle practically does not change. The relieved spindle may then be braked in a simple manner. Since the pressure roller moves essentially in parallel to the course of the tangential belt, when the pressure roller is in the operative position, the wrap with respect to the spindle which is approached by the pressure roller does not change or does not change significantly, while the angle of wrap of the tangential belt at the spindle, from which the pressure roller moves away, is reduced significantly. In this manner, it is possible to relieve one spindle from the load to an extent which is sufficient for braking, while the driving conditions with respect to the other spindle remain practically unchanged.
In a further development of preferred embodiments of the invention, it is provided that the pressure rollers are each arranged on a swivel arm which can be swivelled around a shaft which is in parallel to the spindle shafts. This shaft of the swivel arm may easily be arranged such that the circular-arc movement follows essentially the direction of the course of the tangential belt when the pressure roller is in operative position. Slight deviations from this course have no significance in practice, particularly if these operating conditions occur only for a short time.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.